Mitral valve repair is the procedure of choice to correct mitral regurgitation of all etiologies. With the use of current surgical techniques, between approximately 70% and 95% of regurgitant mitral valves can be repaired. The advantages of mitral valve repair over mitral valve replacement are well-documented. These include better preservation of cardiac function and reduced risk of anticoagulant-related hemorrhage, thromboembolism and endocarditis.
Nearly all mitral valve repairs include an annuloplasty. The annuloplasty consists of a suture or prosthetic ring that surrounds all or part of the circumference of the annulus of the mitral valve. The annuloplasty serves several functions: it remodels the annulus of the valve; it decreases tension on suture lines; it increases leaflet coaptation; and it prevents recurrent annular dilatation. In addition, the annuloplasty improves repair durability.
Most current annuloplasty techniques require the placement of sutures in the mitral annulus followed by placement of a prosthetic band or ring. This technique can be time-consuming and technically difficult. Furthermore, using current techniques, the annuloplasty requires cardiopulmonary bypass, cardiac arrest, and a large incision in the chest wall and heart.
It is well-known that cardiopulmonary bypass is associated with significant morbidity and mortality. Recognition of the damaging effects of cardiopulmonary bypass has been the impetus for significant advances in beating heart coronary artery bypass grafting. As a consequence, approximately 20% to 35% of all coronary artery bypass grafting is now performed on a beating heart. To date, however, there are no clinically-applicable techniques for performing mitral valve surgery on a beating heart without the use of a heart-lung machine. Therefore, mitral valve repair by annuloplasty currently entails a major operation that includes all of the complications attributable to cardiopulmonary bypass.
In current practice, all patients judged to be candidates for mitral valve surgery must face the risk of cardiopulmonary bypass and cardiac arrest. Therefore, patients early in their disease process (i.e., those who have not yet suffered significant cardiac damage) generally have surgery deferred until they develop troubling symptoms or cardiac dysfunction. Conversely, other patients (i.e., those with poor cardiac function and other co-morbidities) are frequently denied surgery as the risk associated with cardiopulmonary bypass and cardiac arrest is too high.
Mitral regurgitation is common in patients with poor cardiac function and heart failure. It is well known that mitral regurgitation contributes significantly to the debilitating symptoms of such patients. Correction of mitral regurgitation would improve symptoms and, possibly, longevity in such patients. Furthermore, it is believed that mitral regurgitation contributes to the deterioration of left ventricular function. Thus, correcting mitral regurgitation may halt further decline in ventricular function and may, in fact, cause improvement in ventricular function.
Unfortunately, however, such heart failure patients are at high risk for mitral valve surgery using current techniques. By way of example, the operative mortality for mitral valve surgery in patients with left ventricular dysfunction is approximately 5% to 15%. Therefore, the majority of such patients are not deemed candidates for mitral valve repair using currently available techniques.
Development of a system and method for mitral valve annuloplasty that does not require cardiopulmonary bypass would extend the benefits of mitral valve repair to a large segment of the heart failure population.